1. Field of the Invention
This invention relates generally to the field of gas conduit tubes, and more particularly concerns the structure of the end portion of gas conduit tubes, which structure facilitates the connection of telescopically communicating exhaust pipes.
2. Description of the Prior Art
It is an object of most automotive exhaust systems to provide a conduit for directing exhaust gas from the engine to a remote exhaust port. It is common in such exhaust systems that the exhaust gas conduit may link several devices for treating the exhaust gas before passing it to the exhaust port. For example, a typical exhaust system may include a muffler, a resonator, an air cleaner aspirator, a catalytic converter, or any combination of these. It is also common that such exhaust systems must be designed to be compatible with various drive trains, chassis sizes, body styles, and the like. For these reasons, the exhaust gas conduit is generally made up of several exhaust tubes or pipes of various shapes and lengths, which are linked together to form a continuous enclosed path for the exhaust gas to follow.
The most common way of joining pipes to construct an exhaust conduit is to utilize a lap joint, wherein succeeding tubes of smaller end diameter are fitted telescopically into preceding tubes of larger end diameter, and clamped in the region where the tubes overlap. Clamping means which encircle the outer tube are tightened down so as to crimp the outer tube onto the inner tube at the point of overlap.
In order to facilitate the crimping of the outer tube to the inner tube, exhaust tubes generally have one end formed with a plurality of slots running parallel to the longitudinal axis of the tube and extending from the tube end inwardly for a distance of 11/2 to 3 inches. A number of these slots are placed around the circumference of the tube at its end. A typical muffler connecting tube is shown in the patent to Bryant, U.S. Pat. No. 2,825,421. A similar slotted tube end construction is shown in a patent to L. H. Billey, U.S. Pat. No. 3,137,553, for an air cleaner aspirator.
The slots in such outer tube configurations allow the outer tube to be deformed, or crimped, inwardly on an inner tube placed telescopically within the outer tube, by the action of a clamp encircling the outer tube in the region of the slots, more easily than if the tubular wall were unbroken in the clamping region.
This is the most common exhaust tube end construction, and there are several problems with it. The primary problem with such a slotting arrangement is that a slotted tube has a discontinuous, broken end. This broken end is very susceptible to deformation during packaging, handling, and shipping of exhaust tubes. Since the lap joint construction requires fairly close tolerances between the inner diameter of the outer tube and the outer diameter of the inner tube, slight deformations, out of roundness, etc., in the outer tube may make it very difficult, if not impossible, to telescopically fit the inner tube therein.
Another problem with the presently known slotted tube end arises during construction of the tubes. Most exhaust tubes are constructed from aluminized steel flat stock, which is first slotted, then rolled into tubular form and welded along the seam. The heat from the welding operation causes contraction and expansion in the portions of the tube between the slots. This warpage also creates out-of-round and tolerance problems in the finished product.